\(x+\sqrt{4-x^2}=2\)

\(\Leftrightarrow4-x^2=\left(2-x\right)^2\)

\(\Leftrightarrow4-x^2=4-8x+x^2\)

\(\Leftrightarrow4-x^2-4+8x-x^2=0\)

\(\Leftrightarrow8x-2x^2=0\)

\(\Leftrightarrow2x\left(4-x\right)=0\)

\(\Leftrightarrow\left[{}\begin{matrix}2x=0\\4-x=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=0\\x=4\end{matrix}\right.\)

\(x+\sqrt{1-x^2}=1\)

\(\Leftrightarrow1-x^2=\left(1-x\right)^2\)

\(\Leftrightarrow1-x^2=1-2x+x^2\)

\(\Leftrightarrow1-x^2-1+2x-x^2=0\)

\(\Leftrightarrow2x-2x^2=0\)

\(\Leftrightarrow2x\left(1-x\right)=0\)

\(\Leftrightarrow\left[{}\begin{matrix}2x=0\\1-x=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=0\\x=1\end{matrix}\right.\)

a: \(\frac{2x}{x^2+2xy}+\frac{y}{xy-2y^2}+\frac{4}{x^2-4y^2}\)

\(=\frac{2x}{x\left(x+2y\right)}+\frac{y}{y\left(x-2y\right)}+\frac{4}{\left(x-2y\right)\left(x+2y\right)}\)

\(=\frac{2}{x+2y}+\frac{1}{x-2y}+\frac{4}{\left(x-2y\right)\left(x+2y\right)}\)

\(=\frac{2\left(x-2y\right)+x+2y+4}{\left(x-2y\right)\left(x+2y\right)}=\frac{2x-4y+x+2y+4}{\left(x-2y\right)\left(x+2y\right)}\)

\(=\frac{3x-2y+4}{\left(x-2y\right)\left(x+2y\right)}\)

b:Sửa đề: \(\frac{x^2}{x^3-4x}+\frac{6}{6-3x}+\frac{1}{x+2}\)

\(=\frac{x^2}{x\left(x^2-4\right)}-\frac{6}{3\left(x-2\right)}+\frac{1}{x+2}\)

\(=\frac{x}{\left(x-2\right)\left(x+2\right)}-\frac{2}{x-2}+\frac{1}{x+2}=\frac{x-2\left(x+2\right)+x-2}{\left(x-2\right)\left(x+2\right)}\)

\(=\frac{2x-2-2x-4}{\left(x-2\right)\left(x+2\right)}=\frac{-6}{\left(x-2\right)\left(x+2\right)}\)

c: \(\frac{x^2+2}{x^3-1}+\frac{x}{x^2+x+1}+\frac{1}{1-x}\)

\(=\frac{x^2+2}{\left(x-1\right)\left(x^2+x+1\right)}+\frac{x}{x^2+x+1}-\frac{1}{x-1}\)

\(=\frac{x^2+2+x\left(x-1\right)-\left(x^2+x+1\right)}{\left(x-1\right)\left(x^2+x+1\right)}\)

\(=\frac{x^2+2+x^2-x-x^2-x-1}{\left(x-1\right)\left(x^2+x+1\right)}=\frac{x^2-2x+1}{\left(x-1\right)\left(x^2+x+1\right)}\)

\(=\frac{\left(x-1\right)^2}{\left(x-1\right)\left(x^2+x+1\right)}=\frac{x-1}{x^2+x+1}\)

Số tiền Minh đã dùng để mua là:

3000 + 4000 = 7000 (đồng)

Số tiền còn lại của Minh là:

10000 - 7000 = 3000 (đồng)

* Bác bán hàng có thể trả cho Minh:

+ Tờ bạc 2000 đồng và 1000 đồng

+ 3 tờ bạc 1000 đồng

...

Chúc bạn học tốt!! ^^

1 The boys like playing video games

2 My mother doesn't like listen to music

3 You should eat more fresh fish, which makes you smarter

4 He had a headache last night, sho he didn't sleep well

5 Doing exercises makes you healthier

6 My dad enjoys planting trees

The boys like playing video games

 My mother doesn't like listen to music

 You should eat more fresh fish, which makes you smarter

He had a headache last night, sho he didn't sleep well

 Doing exercises makes you healthier

My dad enjoys planting trees

1 will have - will invite

2 goes

3 play

4 won't study

5 does

6 will travel

7 won't come

8 will come

bài 2

1 riding - walking

2 swimming

3 watching

4 tell

5 travel

6 studying

7 seeing

8 go - have

1. She likes playing guitar

2. He likes reading book

3.She likes singing 

4.He likes playing soccer

CuO + H2 -> Cu + H2O

0.01              0.01

FexOy + yH2 -> xFe + yH2O

Fe            +        2HCl ->     FeCl2 +           H2

\(\)0.02                                                          0.02                                              \(\)

Cu + HCl -> (không phản ứng)

nH2 = 0.02mol => mFe = 1.12g

=> mCu = 1.76 - 1.12 = 0.64g => nCu = 0.01mol

=> mCuO = 0.8g => mFexOy = 2.4 - 0.8 = 1.6g

Ta có: 56x + 16y -> 56x

             1.6g       -> 1.12g

=> \(1.6\times56x=1.12\times\left(56x+16y\right)\)

=> \(26.88x=17.92y\Leftrightarrow\dfrac{x}{y}=\dfrac{2}{3}\)

=> Fe2O3

\(log_{\sqrt{x}}y=\dfrac{2y}{5}\Rightarrow2log_xy=\dfrac{2y}{5}\) \(\Rightarrow log_xy=\dfrac{y}{5}\)

\(log_{\sqrt[3]{5}}x=\dfrac{15}{y}\Rightarrow3log_5x=\dfrac{15}{y}\Rightarrow log_5x=\dfrac{5}{y}\)

\(\Rightarrow log_xy=\dfrac{1}{log_5x}=log_x5\Rightarrow y=5\)

\(\Rightarrow log_5x=\dfrac{5}{5}=1\Rightarrow x=5\)

\(\Rightarrow x^2+y^2=25+25=50\)

Chọn B

Chọn D

tai sao vay a?